Absolutely crap social skills with the opposite gender

My advice is to stop looking at guys as guys and look at them as people. Being critical about how you think you were perceived (calling yourself a bitch, supporting it with what you think is wrong about you) is you dragging yourself down. When you do that, you're telling your brain not to develop the capacity. There are cultural norms you can practice, but there's no guide for presenting yourself.
Also when you do find yourself chatting with a guy, don't worry about talking about yourself or not talking. Focus on listening and engage, it gets easier with practice. Unless you're the kind of person who comes into a conversation about hot dogs talking about your new car, it's okay to share relevant topical thoughts.

So super simple version:
Be nice to yourself, your brain will follow.
Remember guys are just people.
Be yourself in conversation.
Listen and engage.

Good luck!

Relaxing is the solution. How to relax? Relax, focus on your breath and mentally don't worry. Tell a guy the most embarrassing thing you can think of and watch the world not collapse

@KiwiWisdom makes are great point saying look at guys as people not guys. Also my advice to you is to "by yourself" as guys love women that are themselves.

By the way most guys are not very judgemental at all, most of us can talk about anything. If a guy is talking to you try to think of a question you can ask him based on what he is talking about. It is ok to talk about yourself. Just listen to what he is saying, ask him related questions and just let the conversation flow from there. Most men understand when women come across as shy and most men will not judge women for that. The truth is you are more likely to make him think "Well she is shy but I have to give her credit for trying to overcome her shyness and talk to me."

It is best to be yourself. That way a guy can see your personality. Don't feel bad if your personality does not connect with some guys. That is one guy, people's personalities are different and not every person is going to connect with every other person.

I wish you luck. :)

I'm self concious too, but the more you pratice (I misspelled that and it suggested prattle haha) the easier it gets.

I find the people who gab all the time tend to also have poor social skills. Socializing isn't about just saying as much as you can, so don't feel bad.

You should try involving yourself in gender neutral activities (eg. cooking lessons, volleyball, some language class), because you won't fix anything just staying in your comfort zone. You basically have to jump in with both feet to become better at socializing.

Btw guys are easy to talk to, nothing is a bad topic for us.

Cute.